1. Field of the Invention
The present invention relates to a vacuum chuck and a sucking plate used to suck an object to be sucked, such as semiconductor wafers, so that heat treatment, a grinding process, a polishing process, a CVD process or a PVD process, such as sputtering, for example, can be carried out on the object to be sucked. In particular, the invention relates to an appropriate vacuum chuck and sucking plate preferably used to polish the surface of semiconductor wafers and the like.
2. Discussion of the Background
In general, in manufacturing a semiconductor product, a single crystal silicon ingot is thinly sliced, and after that, the surface of the slices is ground, lapped and polished, and thereby, silicon wafers polished to a mirror surface can be gained.
This step of grinding/polishing a silicon wafer is an indispensable, important step for manufacturing precise semiconductor products (semiconductor chips), and in this step of grinding/polishing a silicon wafer, it becomes necessary a wafer grinding/polishing apparatus where a silicon wafer is secured and ground/polished. For this reason, various types of conventional wafer grinding/polishing apparatuses have been proposed.
Wafer polishing apparatuses where a semiconductor wafer is bonded to the holding surface of a wafer holding jig using an adhesive and then polishing is carried out have been used as a conventional apparatus (see for example JP-A 11-320394).
FIG. 1 is a cross sectional view schematically showing an enlarged portion of an example of a conventional wafer polishing apparatus. As shown in FIG. 1, this wafer polishing apparatus 700 is comprised of: wafer holding jigs 701 in disc form which are configured so as to hold semiconductor wafers 715 downward and let these semiconductor wafers 715 make contact with a polishing surface 725a of a table 725, and after that, rotate, so that the surface of semiconductor wafers 715 is polished; and a rotatable table 725 having a polishing surface 725a. 
A pusher rod 724 is secured to the center portion of the surface on the side opposite to the holding surface 721 of a wafer holding jig 701, and this pusher rod 724 is connected to a driving means, not shown, so that the pusher rod 724 and the wafer holding jig 701 rotate when this driving means is driven. In addition, the semiconductor wafer 715 adheres to and is held by interposing an adhesive layer made of a thermoplastic wax and the like formed on the holding surface 721 of the wafer holding jig 701.
Upon polishing semiconductor wafers 715, the wafer holding jigs 701 and the table 725 are rotated, and then, the wafer holding jigs 701 or the table 725 is moved upward and downward, so that the semiconductor wafers 715 and the polishing surface 725a of the table 725 are contacted to each other, and thereby, the semiconductor wafers 715 are polished.
Moreover, polishing apparatuses using a vacuum chuck for making attachment and removal of a semiconductor wafer easy have been proposed (see for example JP-A 2000-15573).
In addition, vacuum chucks having a porous ceramic plate and an outer periphery sealing layer made of a dense ceramic which is glass joined to the outer periphery of this porous ceramic plate have been proposed as another type of wafer grinding/polishing apparatus (see for example JP-U 2555938).
Specifically, a vacuum chuck as that shown in FIG. 2 is disclosed. That is to say, a vacuum chuck made of a sucking body is disclosed, where porous ceramic 501 in disc form which is impregnated with low melting point glass 504 in the peripheral portion and on the upper surface of which a suction surface 501a is formed is fitted to an outer periphery sealing layer 502 in the cylindrical form having a bottom having air sucking portions 506 made of a dense ceramic, and the border portion between these is glass joined with low melting point glass 505.
Further, in order for the wafer grinding/polishing apparatus to suck wafers of different sizes, wafer grinding/polishing apparatuses have been proposed, where a porous body made of a porous ceramic or sintered plastic, for example, is used as the suction table, and a layer made of an air blocking epoxy resin is formed on this suction table through impregnation or application (see for example JP-A 6-143073 and JP-A 8-39376).
In addition, wafer grinding/polishing apparatuses which can handle wafers of different sizes (universal chuck mechanism) have also been disclosed (see for example JP-A 3-32537, JP-A 8-1464, JP-A 8-148548, JP-A 9-174364 and JP-A 2000-232083).
Universal chuck mechanisms as that shown in FIGS. 3A and 3B are disclosed as specific examples. That is to say, a universal chuck mechanism having (A) a plate for attaching a wafer 625 where an air permeable porous ceramic disc 622 is formed at the center, a number of air permeable porous ceramic annular bodies 623a, 623b, 623c and 623d having the same center and the same height are arranged around the outer circumference of this disc and air impermeable thin film annular partitions 624a to 624d having a width of several mm and the same height as the above-described disc are arranged between the above-described air permeable porous ceramic disc 622 and air permeable porous ceramic annular body 623a, as well as between these air permeable porous ceramic annular bodies 623a to 623d, and all of these members form a single disc, (B) a frame for housing the plate for attaching a wafer 630, having a recessed annular edge portion 626 for housing a plate for attaching a wafer 625 on the upper surface, where a concave portion 627 is provided at the center of the upper portion, which is located on the lower side of the plate for attaching a wafer 625, a number of annular grooves 628a to 628d serving as a path for a fluid are provided in concentric circles with the concave portion 627 at the center, and a number of air sucking holes 629 are respectively provided in the vertical direction in these annular grooves, and (C) a securing base 631 having air sucking portions which are connect to the annular grooves 628a to 628d which are provided in the plate for attaching the wafer 625, to which the frame for housing the plate for attaching a wafer 630 can be secured is disclosed.
The contents of JP-A 11-320394, JP-A 2000-15573, JP-U 2555938, JP-A 6-143073, JP-A 8-39376, JP-A 3-32537, JP-A 8-1464, JP-A 8-148548, JP-A 9-174364 and JP-A 2000-232083 are incorporated herein by reference in their entirety.